PICRIC ACID Ig
Picric Acid (Trinitrophenol), C0H9(OH)^No! 4 1 '
Woulfe, 1771 ; Schmidt, Glutz, Bcr^ 1869, 2, 52. * I
25 grms. phenol. l|^
25 „ cone, sulphuric acid. \'fl
i QQ „ (70 c.c.) cone, nitric acid, sp. gr. 1*4. - j*
25 „ (20 c.c.) fuming nitric acid, sp. gr. 1-5. |'
The phenol and concentrated sulphuric acid are heated ,<' i
together in a ])orcclain basin for a few minutes, until a clear V*
solution of phenol sulphonic acid is obtained. It is diluted. '*
with half its volume of water, well cooled, and then slowly 4
added, in small quantities at a time, from a tap-funnel, to the ^
nitric acid contained in a flask (r litre), and well shaken.*- \f
The liquid assumes a, deep red colour, a considerable rise of If
temperature occurs, and red fumes are evolved. When the -f*
phenol sulphonic acid has been added, the flask is placed on. *d
the water-bath and heated, with the addition of 25 grams fuming-
nitric acid, for i.....2 hours.* On cooling, picric acid separates
out as a yellow, crystalline mass. It is diluted with water,
filtered at the pump, and washed free from the mother liquor
with cold water. It is then purified by recrystallisation from a
large quantity of hot water acidified with a few drops of
sulphuric acid. Yield, about 30 grains.
CJ l,(011) +1 F,SO., - C0H4(0H).S03H + H20.
C(;Ha(OH)(NOa)3 + 3H20 + H2SO4. if
Properties.-—Yellow, prismatic crystals; m. p. 122*5°; sub- ^i
limes on gently heating ; explodes on detonation ; easily soluble
\\\ alcohol and ether ; with difficulty in cold, more readily in f|
hot water ; the solution has a bitter taste.
Reactions.— r. To an aqueous solution of picric acid add a
little potassium cyanide solution, and warm. A brown crystal-
line precipitate of isopurpuric acid separates.
2. Add picric acid and a few drops of caustic socla to a dilute
solution of grape sugar, and warm. The liquid turns deep brown.